Tag Archives: Diagnostic test

Scoring systems

Clinical, General paediatrics

As usual, any system that has reasonable sensitivity has rubbish specificity (negative predictive value).  Retrospective analysis of 9000 UK A&E attendees <15yrs –

  • a modified Yale Observation Scale (YOS) – sensitivity of 54.0% and specificity of 63.7% at a cut-off of 10.
  • Pediatric Advanced Warning Score (PAWS) – sensitivity of 58.0% and specificity of 81.3% if any ‘red’ sign was present.
  • Alert, Voice, Pain, Unresponsive (AVPU) scale;
  • Recognising Acute Illness in Children (RAIC) score; sensitivity of 76.0% and specificity of 6.2% for ruling out serious bacterial infection at a score of 5 or less.
  • Oxford Vital Signs score sensitivity of 80.0% and specificity of 49.3% if any sign was present.
  • 2007 version of NICE CG160 (Fever guideline) traffic light system. 100% sensitivity and specificity on 0.12% if any ‘amber’ or ‘red’ sign was present, and had sensitivity of 62% and specificity of 74.5% if any ‘red’ sign was present  But data available covered only a selection of red and amber features.

[Verbakel, Pediatric Emergency Care 2014; 30: 373–80]

Same author applied rules to different data sets across UK, Netherlands and Belgium, found that all had lower performance than in their original derivation studies, but also wide variation across datasets eg NICE CG160 specificity ranged from 1-28.7%! Hard to understand differences.  [BMC Medicine 2013; 11: 10]

Lacour scoring system (“Laboratory-Score”) based on CRP, PCT and urinalysis. Has sensitivity of 94%, spec of 81%. Would reduce incidence of antibiotic use from 65 to 40% but good enough? [Lacour, PIDJ 2008 PMID 18536624]

 

UTI Follow up investigations – GGC guideline 2020

Clinical, Common, General paediatrics

Same definitions of upper, lower and atypical. UTI definitions

  • Under 6/12, USS for all, within 6 weeks. Urgent if recurrent or atypical features (other than funny bugs).

UTI imaging under 6 months

  • Provided things settle within 48 hours of treatment, no further investigations are required unless atypical or recurrent, in which case everyone gets DMSA (6 months after infection) and MCUG.
  • 6/12 to 3yrs: USS only if doesn’t settle within 48 hours of treatment. If atypical or recurrent then USS and DMSA (USS urgent if atypical features, other than funny bugs), else within 6 weeks.

UTI imaging 6/12-3yrs

  • Consider MCUG if dilatation on US, or family history of VUR, or atypical bugs, or poor flow. (MAG3 if continent)
  • Over 3yrs: same, except no DMSA even if atypical features, and no mention of MCUG at all.

UTI imaging 3yrs+

If USS abnormal, refer for consideration of further imaging.

But:

  • USS – not much evidence for benefit, esp if normal antenatal scan, rarely changes management even if something minor found, but harmless. If dilatation seen, do MCUG urgently.
  • MCUG – like GORD, maybe you see reflux, maybe you don’t, so can you rely on it? NB Cost, radiation, discomfort…
  • DMSA – acutely, diagnoses pyelonephritis. Then remain positive for up to 6 months after an infection. Late scan diagnoses scars. But if negative during first UTI episode, rarely (NPV 88%) have VUR and never high-grade VUR. [J Pediatrics Volume 150, 1 , January 2007, 96-99]
  • Antibiotic prophylaxis – not routinely.  If considered on the basis of risk/benefit discussion, then use trimethoprim.  If trimethoprim resistance, consider strategy of early empirical treatment rather than use a broad spectrum antibiotic such as co-amoxiclav or cefalexin (else risk of highly resistant bugs). [Hoberman A, NEJM 2003] Review every 3-6 months.
  • Cycling of antibiotic for prophylaxis may be more rational eg every 2-4 weeks

Studies do not address whether placebo or nothing is worse than prophylaxis (Cochrane: suggests about 36% reduction in infection, but all 3 studies biased, and most other work has prophylaxis vs surgery). Eg Sweden, only screen if additional risk factor, and v low prevalence of scars. Garin study (Paeds 2006) non placebo controlled, found no protection from recurrent infection with antibiotic prophylaxis (the rate for those with reflux was close to significance but seemed to be cystitis rather than pyelo) – plus the bugs were resistant. The rate of scarring was actually higher in the prophylaxis group…

[(Roberts, Kenneth) PIDJ 23(12); 2004:1163-1164 ]

UTI Follow up investigations – NICE CG54

Clinical, Common, General paediatrics
  • Under 6/12, OPD USS sufficient if good response to treatment within 48 hours.
  • Under 6/12 and atypical (see below) or recurrent (see below), then urgent USS to look for obstruction or severe reflux, or if simply non-E.coli then within 6 weeks.  PLUS later OPD DMSA (ie 4-6 months post infection), MCUG.
  • 6/12 to 3 yrs: nothing if good response to treatment within 48 hours. If atypical or recurrent, as above but no MCUG unless:
    • family history,
    • poor flow,
    • dilated tract on US,
    • non-E coli.
  • Over 3yrs: nothing if good response to treatment within 48 hours. If atypical, only needs urgent USS (OPD USS within 6 weeks if simply non-E.coli). If recurrent, do OPD USS and later DMSA.

Atypical defined as seriously ill, poor urine flow, abdominal/bladder mass, raised creatinine, septicaemia, failure to respond to appropriate antibiotics within 48 hrs, non-E. coli infection

Recurrent defined as 3 lower tract UTIs, else 1 upper tract plus any other

If another UTI occurs before the DMSA is done, don’t defer DMSA in case scarring already established.

Prophylactic antibiotics for MCUG (1 day before to 1 day after).

UTI diagnosis

Clinical, Common, General paediatrics, Infectious disease

See NICE 224 (2022).

Classic symptoms – dysuria, frequency, new wetting, dark or cloudy or smelly urine.  Frank haematuria, loin pain.  Fever, shivering (rigors), history of UTI. 

Clean catch ideally, pad (commercial, not cotton wool balls or gauze) if clean catch unsuccessful. Else catheter.  Suprapubic aspiration is an option but needs ultrasound to confirm bladder full.

See Sofia method of urine collection.

 

Testing

Under 3 months – send for culture and microscopy. Urgent?

Microscopy interpretation is simply on basis of pyuria pos/neg, bacteria pos/neg.

Over 3/12, dipstick is standard. A positive dipstick urinalysis for BOTH leucocyte esterase (LE) and nitrite is specific, negative both is a good negative predictor. If dipstick positive for just one, not reliable either way. Metanalysis, Huicho Luis, PIDJ 2002;21:1-11. Previous metanalysis by Gorelick and Shaw (Peds 1999) concluded nitrite/LE tests superior to microscopy!

If nitrites and leucocytes positive, assume infection. Culture only if high risk for serious infection or recurrent UTI.

Nitrites only positive, treat but send culture.

Leucocytes only positive, send culture, treat if classic UTI symptoms or under 3yrs, else await result before treating.

Culture if high risk of serious illness, upper tract signs, poor response to treatment, recurrent UTI.

Most studies show that clean catch is equivalent to suprapubic aspiration (SPA); limited data on pad, nappy or bag specimens.

Uricol (Euron, Newcastle) urine pads. Check at 10 min intervals (discard after 30mins). Cost 18p each. Agrees with clean catch for gluc/ket/blood/nitrite (within 1 block ) but in study only 2 cases with leucocytes so ?reliable.

Health Technology Assessment (Winchester, England). 10(36):iii-iv, xi-xiii, 1-154, 2006 Oct.

Helicobacter – Testing

Gastro, General paediatrics

Who Should Be Tested? See Helicobacter.

Refractory iron-deficiency anaemia is not considered a good reason for testing anymore.

Gold standard is Gastric biopsies (antrum and corpus) for histopathology during endoscopy. Initial diagnosis of H. pylori infection can be based on either positive histopathology + positive rapid urease test, or a positive culture.

Stool antigen test is pretty reliable. Could simply indicate asymptomatic carriage though. Once you know about it, of course, you need to consider eradication given cancer risk.

You should wait at least 2 weeks after stopping proton pump inhibitor (PPI) therapy and 4 weeks after stopping antibiotics before doing any of these tests.

Detection of antibodies against H. pylori (whether in blood, urine, saliva) are not reliable for use in the clinical setting.

 [ESPGHAN and NASPGHAN. Evidence-based guidelines J Pediatr Gastroenterol Nutr. 2016]